1. Technical Field
The invention relates generally to image processing systems, and, more particularly, to image processing systems that allow a user to create and view panoramic three dimensional images from data representing multiple views of a scene.
2. Description of the Related Art
Conventional three dimensional graphics applications and associated hardware render scenes composed of one or more three dimensional objects. The objects are typically represented by geometric primitives, for example triangles. The objects are represented by graphics data that represent the position and color of primitives in a model coordinate system. The graphics system renders the scene to display those object(s) of the scene that are visible in a viewing window based upon a view point. The user can navigate through the scene by changing the position and orientation of a view point reference (camera). In addition, animations can be performed by navigating through a series of preselected positions and orientations of the view point reference.
The rendering operation is a computationally intensive process and, thus, typically performed by specialized graphics hardware. Such systems are powerful yet remain costly due to the need for specialized hardware dedicated to this purpose.
Moreover, conventional three dimensional graphics systems require that the user provide a three-dimensional model of the scene (i.e., graphics data that represents the position and color of the geometric primitives of the scene in the model coordinate system). Such models may be created with software in conjunction with peripheral devices (pen tablets, scanners, cameras, etc). For example the software sold under the name CATHA by Daussault of France allows a user to build a three-dimensional model of a scene. However, such modeling software is expensive and, in addition, a significant investment in labor may be required to model even a relatively uncomplicated scene.
Because of the high costs associated with conventional three dimensional graphics systems, alternative solutions have emerged that provide effective yet limited capabilities in creating and viewing a three dimensional scene which are suitable for use on standard personal computers and without the need for dedicated graphics hardware. One such solution is the software developed and sold by Apple Computer, Inc. of Cupertino, Calif. under the name QuicktimeVR. The QuicktimeVR software is segmented into two distinct packages. The first package, which is sold to content providers, is an authoring tool that allows content providers to develop a panoramic three-dimensional image from multiple views of a scene. The second package is a viewer which is distributed to consumers and which allows the consumer to view the panoramic three-dimensional images created by the authoring tool. A more detailed description of the operation of the QuicktimeVR system may be found in Chen, "Quicktime.RTM. VR--An Image-based Approach to Virtual Environment Navigation", SIGGRAPH 1995, Los Angeles, Calif., pp. 29-38, and in U.S. Pat. No. 5,396,583 to Chen et al., which is assigned to Apple Computer, Inc.
The QuicktimeVR system utilizes a cylindrical environment map to represent the panoramic view of a scene (or collection of images). Different perspective views are rendered by mapping the cylindrical environment map to a desired viewing window. However, one of the limitations of the QuicktimeVR system is that the authoring tool does not have capability of mapping top and bottom images of a panoramic scene to the cylindrical environment map. Thus, the viewing tool lacks the ability to render views of the panoramic scene that includes any portion of such top and bottom images, which in effect limits the vertical field of view of the QuicktimeVR system.
For example, consider a cylindrical environment map for a room or scene with four walls, a square floor, and a square ceiling. The four walls may be readily mapped to the cylindrical environment map using methods such as those employed by QuicktimeVR. The data contained in the images of the four walls occupies the interior of a scalloped portion of the cylindrical environment map, as shown in FIG. 12. Without the capability to incorporate data from top and bottom images, the portions of the cylindrical environment map, such as the regions marked by X and * in FIG. 12, cannot be filled with appropriate color values. These regions may be filled with solid black or other arbitrary color or pattern, or the ability to view the data in the cylindrical environment map could be restricted so as to prevent access to any portion of the cylindrical environment map above the lowest points of the upper boundary or below the highest point in the lower boundary.
Thus, there is a need in the art to provide for a cost effective system for generating and viewing three dimensional panoramic images that extend the field of view of the panoramic image, thus providing an improved level of interactive graphical feedback.